1894.] NATURAL, SCIENCES OF PHILADELPHIA. 455 



THE SADSBTJRY STEATITE. 

 BY THEODORE D. RAND. 



Under this name I purpose describing outcrops of steatitic rocks 

 most conspicuously exposed in West Sadsbury Township, Chester 

 County, Pa., in the adjoining township of Sadsbury, Lancaster Co., 

 and less so in Valley, West Cain and West Brandywine Town- 

 ships, Chester Co. These, though known to arch?eologists, seem to 

 have escaped the notice of geologists, though known locally and 

 made use of in the building of lime-kilns, and in the lining of iron 

 furnaces. Long anterior to this use, they were evidently of value 

 to the aborigines, whose tools are still to be found at the outcrops, 

 together with fragments of vessels manufactured by the Indians from 

 the steatite. 



My attention was directed to these exposures by Mr. Harry Wil- 

 son, of Gum Tree, Chester Co., who had visited the localities in the 

 study of archaeology, and who kindly took me to the most prominent 

 outcrops. 



North of the Cambrian sandstone, which forms the mass of the 

 prominent North (Chester) Valley Hill, is a peculiar rock, often re- 

 sembling a pegmatite, often a very feldspathic gneiss or schist, occa- 

 sionally a hornblende or a mica schist. North of this is a very 

 heavy bedded, hard, highly crystalline gneiss, that recognized in 

 this portion of Pennsylvania as the most ancient gneiss, probably 

 of Laurentian age, identical with that of the Highlands of New- 

 Jersey and with that of the ridge which extending southwestward 

 from near Trenton, N. J. , to near Willow Grove, and there bifur- 

 cating, sends its southerly arm southwestward through Montgomery, 

 Delaware and Chester counties to North Brook, five miles southwest 

 of West Chester, and its northerly through northern Chester County, 

 where it widens greatly. It is this northerly arm which is referred to 

 above. In all its extent the rock is very compact and hard unless 

 decomposed, highly crystalline, rarely, if ever, schistose, except 

 from decomposition, and usually showing the characteristic blue 

 quartz. 



